Riociguat, also known as methyl{4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-B]pyridine-3-yl] pyrimidine-5-yl}N-methylcarbamate, has formula (I). Riociguat is the first of a new class of Guanylatecyclase (sGC) agonist, directly activates sGC and increases low levels of NO sensitivity, for treating pulmonary hypertension and chronic obstructive pulmonary hypertension.

Many drugs may exist in different crystalline forms, which may have significant differences from each other inappearances, solubilities, melting points, dissolution rates, bioavailabilities, stability, efficacy and the like. So it is very important to think through the situation of different crystal forms in drug development.
The compound of formula (I) is first disclosed by U.S. Pat. No. 7,173,037, wherein example 8 discloses the preparation method of the compound of formula (I) wherein a crystal form of the compound of formula (I) is obtained by recrystallization from methanol. US 20110130410 disclosed a DMSO solvate of the compound of formula (I). However, we can't determine the crystal form of formula (I) for the above references do not fully characterize the polymorphs by XPRD, DSC, IR etc and their solubility, stability behavior in drug formulation.
Therefore, the crystalline behavior of formula (I), methyl{4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-B]pyridine-3-yl] pyrimidine-5-yl}N-methylcarbamate, need to be well investigated to obtain the desired crystal form in order to fulfill the formulation requirements.